Concrete in History and Architecture

You can have a conversation with concrete. The beauty of what you create comes if you honor the material for what it really is.​--Louis Kahn, 20th century Estonian-American architect

Teshima Museum, Teshima, Japan, by Ryue Nishizawa​

It might not be much to look at when you're watching people work with it, but concrete is not just powdered rock. Calcium carbonate, formed from the compressed remains of million-year-old organisms, heated and squeezed by the movements of the Earth's crust, usually in the form of limestone or certain types of clay, is necessary. Heating the limestone or clay in a furnace at about 1450 degrees Celsius causes it to leave a gray-white powder, cement.

Once cooled, cement powder can be added to water, which creates conditions for fibrils of calcium silicate to grow and mesh like crystals to create strong bonds. Cement in smaller amounts is used to set stones or bricks together. Adding sand or gravel creates concrete. In larger amounts, poured into molds, it will create a continuous structure. Engineers and designers will introduce joints in larger structures to compensate for the expansion and contraction of different portions at different times of the day due to heating and cooling.

Roman engineers made use of volcanic ash and lime in the same way modern builders use concrete. They found that they could only use it for portions of structures that were under compression, however. Under tension, concrete develops cracks and fails. Modern engineers use steel reinforcement rods to build with concrete for structures under both compression and tension.

Concrete never completely dries out. Water is a necessary ingredient of concrete. When concrete sets, it is reacting with the water on a chemical level. This also allows it to bond to steel reinforcement rods in larger structures. Regrettably, the presence of water will also cause the steel to rust over time. The expansion of trapped water when it freezes to ice also creates cracks in the material. While inexpensive and easy to produce in large amounts, concrete also requires maintenance to remain safe.

Concrete--private home, Kaunas, Lithuania

Architect Sergey Makhno​Concrete OfficeKiev, Ukraine

Updated: 8 August 2017

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